Combined automatic and manual telephone system.



T. G. MARTIN.

COMBINED `AUTOMATIC AND MANUAL TELEPHONEVSYSTEM.

APPLICATION man Nov. 14, 1906. RENEWED AuG.1.191s.

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COMBINED AUTOMATIC AND MANUAL TELEPHONE SYSTEM.

APPLICATTON FILED NOV. I4. 1906. RENEWED AUG.,1. y1918.

Patented Apr. 22, 1919.

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T. G. MARTIN.

COMBINED AUTOMATIC AND MANUAL TELEPHONE SYSTEM.

APPLICATION man Nov. 14. 190e. RENEwEn Aue. 1.

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NTTE TATES PATEN T @FTTCEO TALBOT G. MARTIN, 0F CHICAGO, ILLINOIS, ASSIGNOR, BY MESNJE ASSIEGNMENTS TO AUTOMATIC ELECTRIC COMPANY, A CORPORATION 0F ILLINOIS.

COMBINED AUTOMATIC AND MANUAL TELEPHONE SYSTEM.

t ,31191,5S4L.,

Application led November 14,

To all wko/)L it may comer/n.'

Be it known that I, TAno'r G. MARTIN, a citizen of the United States of America, and res-ident of Chicago, Cook county, ltllinois, have invented a certain new and useful Imiroveinent in Combined Automatic and bianual Telephone Systems, of which `the following is a specification. i

My invention contemplates a telephone system in which one and the same trunk line can be employed by'either automatic or manual subscribers of one exchange for calling automatic subscribers of another eX- change. It also contemplates certain novel features and details of construction and combinations by which said trunk line can be made busy when used by either automatic or manual calling subscribers for connecting with anautomatic subscriber, so as to protect the same against seizure by other subscribers; by which the originating operator, when a manual subscriber calls an automatic subscriber of the other exchange, over said trunk line, has full supervision of thetrunk connection thus established between her calling subscriber and the called subscriber of the other exchange; and by which the elticiency and service of a system of this particular character will be improved generally.

In the accompanying drawings, Figurel shows in diagram a section of one exchange comprising both manualand automatic apparatus. An ordinary line operators twostrand cord circuit is shown at A and at B is shown a trunking operators cord circuit embodying certain novel features. An automatic subscribers station is sho-wn at C', an automatic selector switch at D, and a repeater at E which also embodies certain novel features to be described.

ll ig. 2 is a diagram representing a section ol a second exchange comprising a common battery connector F, a called subscribers selector at D', and a called automatic substation at C. Between the exchanges .#1 and #2, indicated in Figs, l and 2, respectively, there are provided trunk lines (only one of which is shown) comprising the conductors t and known as the vertical and rotary trunk connectors.

r ig. 3 is a perspective diagram or the conncctor.

The cord circuit at A is an ordinary and well-known line operato1"s cord circuit pro- Specication of Letters Patent.

Patented Apre 22, 1919..

1906, Serial No. 343,409. Renewed August 1, 1918. Serial No. M'tg.

vided with an answering plug c and a calling plug d. A section of the said cord circuit, on the side of the answering plug, is omitted, as it is well understood by those skilled in the art. The section on the side of the calling plug d is shown in order that the details may be more readily understood. The said cord circuit A is provided with an order key c of a suitable or well-known design, whereby the operator 4at the cord circuit A may communicate with the trunking operator at the cord circuit B. Among the details shown in connection with the cord circuit A there are the tip and sleeve supervisory relays 2 and 3, the busy test relay 4, the operators talking set comprising the transmitter 5, receiver 6 and induction-coil the latter .having the primary winding 7 and the secondary winding 8. The operators key is shown at g and the ringing key at t, used in connection with the ringergenerator z'. The tip and sleeve condensers 9 and 10' are also shown, which divide the cord circuit into two inductively united sections. The battery B is shown for providing current to the manual subscribers and operators, and ashaving its positive terminal preferably grounded at Cr.

The cord circuit B of the trunking operator has many of the wellknown features of such a circuit, among which are the terminal jack and the repeating coil 7c comprising the windings ll and l2, and 13 and 14. It will be understood that the said jack is connected with the cord B by a trunk line running from the cord to the board or position of the originating operator. The trunking operators talking set comprises the transmitter l5, the primary winding 16 and secondary winding 17 of the induction- There is also a supervisory lamp 18 for indicating not only when the cord B is in use, but also when the trunlr line @#5, to which the said cord is allotted is being used by an automatic subscriber. There is, irthermore, an automatic calling set m for operating the automatic switches at errchange .711:2 (Fig. 2), a couple or auxiliary relays 19 and 20 which are used in supervision and in initiating a release of the automatic switches, and an alternating current relay p whereby, after the trunlring operator E passes supervision tooperator A, the latter may, by throwing ringing current out on the plug (i, operate to groundltl ico the vertical trunk leading to the connector F and energize the ringer relay of the connector to signal the called subscriber. The said operator B is, of course, provided with a key 'It to correspond with the order wire key e ot' the operator A., whereby the operator at the cord circuit B may connect with the operator at A when a signal is sent over the order wire by the latter.

rlhe automatic substation C may be of any known or approved type, and as shown comprises a receiver 21 and switch-hook 22, for controlling certain substation circuits, a transmitter 23, an induction-coil 24 having the primary and secondary windings 25 and 26, respectively, nected with a condenser` 28, a signaling button 29 for controlling the spring 30 with respect to the contact points 31 and 32, a calling device comprising push-buttons 33 and 34, their respective alloted springs 35 and 36, and the contact points 37 and 38 and the ground post 39. 'For releasing the automatic apparatus after it has been put in use there are provided three release springs 40, 41 and 42. rl`he calling device, although indicated in the apparatus above described, may be of any approved type, but for the purpose ot disclosing the principles of my invention it will be sutliciently clear to represent the apparatus as described.

T he selector switch l) may also be of any known or approved type. In Fig. 1 a selector of the general type disclosed in Patent No. 815,321, granted March 13,1906, to Keith, Erickson and Erickson is shown. The switch-shaft is noti indicated, but the switch-shaft wipers 43, i4 and 45 are shown, together with the vertical and ro- .tary line relays 46 and 47, the bridge-cutoff relay 48, the rotary magnet 49, the vertical magnet 50, the release magnet 51, backrelease relay 52, the private magnet 53, and the side switch comprising the side switch wipers 54, 55, 56 and 57.

The repeater E is a switching device allotted to the trunk line which is accessible y from both a selector D and the trunking operators circuit B, and as shown is inserted between the selector bank terminals which the switch-shaft wipers 43, 44 and 45 engage and the interexchange trunk line con-v ductors t and b. lt comprises a couple of line relays 58 and 59, a dierential relay 60 with a couple of windings 61 and 62, and two additional auxiliary relays 63 and 64 for' controlling certain circuits to be described. The main circuit that passes through the repeater E is divided into two sections, Very much like the operators cord circuit A, by a couple ot condensers 65 and 661.

The connector F, shown in Figs. 2 and 3, is an improvement on the connector disclosed in United States Patent No. 815,176, granted March 13, 1996, to Keith, Erickson and ringer 27 con-I Leonesa Erickson, being an adaptation of the connector shown in said patent to connnon battery work, and comprises the well-known switchshaft 67, switclnshat't wipers 68, 69 and 70, the line and private banks 71 and 72, the vertical and rotary line relays 73 and 74, differential relay 75 having windings 76 and 77, and back-bridge relay 78, the latter bein double-wound and comprising the win ings 79 and 80. The vertical magnet- 81 and rotary magnet 82, which are controlled by the vertical and rotary line relays 73 and 7 4,are used respectively tor operating the switch-shaft 67 in a vertical direction and in a rotary direction. rl`he release magnet 83 constitutes part ot the means by which the switch is restored.v There are in addition the private magnet 84 and the ringer relay 85, both ot which are well known. The private magnet operates to control the side switch Gr while the switch is being used for calling. Said side switch comprises the usual side switch wipers 86, 87, 88 and 89.

Since the selector D and the substation C/ are duplicates of the selector D and the substation C, respectively, no further eX- planation is required with respect --tothe construction thereof. By 'following up the operations of this system when one subscriber calls another, the circuits will be more clearly understood. rl`hese operations are as follows: Y

'llhe operation whereby one automatic sub# scriber calls another automatic subscriber does not require the assistance of a 'manual operator; but when a manual subscriber wishes to call an automatic subscriber it is otherwise. For example, if the automatic subscriber at substation C wishes to call the automatic subscriber at substation C, which will be designated as substation :#5220, he does so of his own accord by operating his calling device in such a manner that the vertical and rotary line conductors 90 and 91 are grounded in accordance with the digits ot' the called number. For example, for the digit 2 the vertical button 33A is pressed twice, whereby the vertical line conductor 90 is lgrounded twice and the rotary button 34 is, after that, pressed once for grounding the rotary line conductor 91. The same operation is repeated with respect to the second digit 2, and also with rpspect tothe digit 0, with the exception t 1a times in the last case The first digit being 2 the subscriber, after removing his receiver 21 from the switch-hook 22 and thus closing connection between the substation ground G2 and the ground post 39, by causing the ground springs 92 and 93 to engage -in contact, presses the vertical button l33 twice, grounding the vertical line Conductor 90 twice liti the vertical button 33 is pressed ten y naar,

through the substation ground G2, as previously stated. As a result the vertical line relay 46 of the selector D is energized, which lattervin turn causes the energization of the vertical magnet 50 for operating the selector switch-shaft, whereby the switch-shaft wipers 43, 44 and 45 are carried opposite the first contact ot the second level of the selector line and private banks (not shown), which level comprises the contacts with which the said wipers are shown engaged in lFig. 1. The energizing circuit for the vertical line relay 46 extends trom the substation ground G2 through the ground springs 92 and 93 to the ground post 39, thence to the vertical line conductor 90, through the side switch wiper 54, Contact point 94 to the vertical line relay 46, thence through the bridgecut-ori'1 relay springs 95 and 96 to `the battery lead 97, and through battery b2 to ground g2. The energizing circuit which is established through the vertical magnet 50 when the vertical line relay 46 energizes and presses the line relay springs 98 and 99 into contact is as follows: From ground G3 through the springs 99 and 98, through the private springs 100 and 101 to the vertical magnet 50, thence to the battery lead 97 and through battery` b2 to ground g2. After the selector D has thus been operated, when the subscriber presses the rotary button 34 once and grounds the rotary line conductor 91 he in turn energizesthe rotary line relay 47 of the selector D by a How oi current from Y the substation ground G2 to the ground post 39, rotary line conduct-or 91, side switch wiper 55, contact point 102, rotary line` relay 47, bridge-cut-otl relay springs 103, 95 and 96 to the battery lead 97, thence through battery b2 to ground g2. The rotary line relay 47 upon energizing carries the line relay spring 104 onto the spring 99, thereby energizing the private magnet 53, once by a lion' of current from ground G3 through the springs 99 and 104- to the private magnet 53, thence through said magnet to battery lead 97, and through battery 52 to ground g2. 'lilhe private magnet upon energizing and deenergizing permits the side switch to pass to second position, thus causing the side switch wiper 57 to engage the grounded contact point 105. As a result a tlow of current is sent through the rotary magnet 49 from ground G4 to the contact point 105, thence through the side switch wiper 57, rotary magnet interrupter springs 106, rotary magnet 49 to the battery lead 97, and through battery b2 to ground g2. 'llhe rotary magnet 49 is energized to carry the shat't wipers 43, 44 and 45 into engagement with the iirst Contact of the second level ot their respective banks. lit the trunlr line leading trom the said nrst set of contacts is not busy the rotary magnet, when it reaches the limit oif its stroke, trips the side a- Lit so that it may pass to third position, thus permanently breaking the energizing circuit for the rotary magnet 49 when the side switch wiper 57 leaves the grounded contact point 105. l3nt itn the iii-st trunk line is busy the Jprivate wiper 45 meets a. grounded contact point and an energizing circuit is set up through the private magnet 53 for reenergizing said n'iagnet while the side switch is in second position, for the purpose of locking the side switch in said second position until the wipers are carried beyond the busy contact or contacts, as the case may be. This energizing circuit for the private magnet extends from the grounded iiirivate bank contact to the private 'wiper 45, thence through the back-release relay ot the sclector D to the side switch wiper contact point 107, private magnet 53 to the battery lead 97, and through battery of to ground g2. Therefore the interruptor comprising the interruptor springs 106 at the rotary varmature 49 produces a series of inipulses for operating the rotary magnet in a step-by-step manner to advance the wipers 43, 44 and 45 as the private wiper 45 continues to meet grounded or busy private contact points; but when the last one is passed, the private magnet renergizes and the side switch is permitted to pass to third position, thus destroying the established energizing circuit for the rotary inagnet 49. Assuming that the selector D operates to carry the line wipers 43 and 44 into engagement with the vertical and rotary trunk conductors 108 and 109, and the private wiper 45 into engagement with the trunk-release conductor 110, when the selector comes to a standstill the subscriberls line conductors 90 and 91 will have been placed in connection with the repeater l@ and a guarding potential established all points from which the repeater may .3e seized, to prevent any interferences. rlhe establishment oi. said guarding potential occurs when the side switch wiper 56 ot the selector D engages the grounded contact point 111, thus placing the private 'wiper 45 in direct connection with the side switch ground A guarding potential thus cstablished is communicated to all selector private banlr contacts that are connected in multiple with the trunk-release comluctor 110, and a How et currentis also thr the auxiliary relay 64 the repeater lil,

whereby the lamp (18 at the cord circuit in is lighted. rl"he circuit for eiicrgizing the supervisory relay may be traced troni the private wiper 45 to the trunk-release conductor 110, thence through the conductor 112 to the supervisory relayl 64, conductor 113, springs 114 and at the trunk operators lrey'o, contact point 116, aruiatu o? the relay 90 to the battery lead r through battery B to ground G.

relay 64 upon energizing accomplishes the following results: It shifts the spring 119 Jfrom the spring 120 and into engagement with the spring 121, whereby the circuit through the lamp 18 is established from groung G6 through the springs 119 and 121, conductor 122, through the lamp 18 to the battery lead 118, and through battery B to ground G. Any operator at the cord circuit B will understand that as soon as the lamp 18 is lighted that trunk is not to be as signed to anyone. When the auxiliary relay 64 at the repeater E energized, in addition to performing the operation that has already been explained, the vertical and rotary trun t conductors 108 and 109 are connected to the rotary and vertical outgoing trung conductors b and a. by the closure of contact between the springs 123 and 124 on one side, and the springs 125 and 126 on the other side.

The second digit being 2 also, the subscriber proceeds, as before, to operate the vertical and rotary buttons 33 and 34, again grounding lthe vertical and rotary line con-- ductors 90 and 91. Grounding the former twice energizes the vertical line relay 58 and the differential relay 60 at the repeater E, the said relay 58 and the winding 61 of the said differential relay 60 being in series. The current flows from substation ground G2 to theV vertical line conductor 90, thencel to the side switch wiper 54 of the selector D, contact point 127, vertical line Wiper 43, vertical trunk conductor 108, vertical line relay 58, Winding 61 of the differential re lay 60 to the battery lead 97, thence through battery b2 to ground g2. Each time that the vertical line relay 58 energizes, the springs 128 and 1.29 are lbrought into engagement, whereby a ground impulse is delivered to the outgoing vertical trunk conductor t from ground G7 at the repeater E, through the springs 129 and 128 and through the springs 130 and 131 of the auxiliary relay 63 to the springs 125 and 126 of the auxiliary relay 64, thence to the outgoing ,Vertical trunk conductor a. The impulses delivered to said conductor a are received at the connector F and the effect will be considered hereinafter. rllhe grounding of' the rotary line conductor 91 by the subscriber energizes in turn the rotary line relay 59 at the repeater E and also the differential relay 60. The energizing current flows from the substation ground G2 to the rotary line conduc tor 91, thence to the side switch wiper 55 of the selector D to the contact. point 132, to the rotary line wiper 44, thence through the rotary line relay 59 and winding 62 of the dierential relay 60 to the springs 133 and 134 of the auxiliary relay 63, and to the battery lead 97, thence through battery 57 to ground g2. The rotary line relay upon energizing forces the line relay spring 135 onto Leonesa the ground spring 129, thereby sending a ground impulse to the rotary trunk conductor I) from ground G7 at the repeater E through the springs 129 and 135, through the springs 136 and 137 ofthe auxiliary relay 63, and through the springs 124 and 123 of the relay 64 to the said trunk conductor b. The said rotary impulse is also directed to the connector F and will bc considered. During the operation of the vertical and rotary line relays 58 and 59 of the repeater E, the differential relay 60 has been energized each time and the differential relay springs 138 and 139 have been separated each' time in order to prevent the impulses delivf ered to either of' the outgoing trunk con.

ductors a or b from passing to the other through the auxiliary relay 63, since there is a normal circuit between the said trunk conductors a and by way of the relay 63 and the differential relay springs 138 and 139, as shown. lt is, therefore, necessary, if it is desired to ground only one of the trunk conductors a or b at a time, that whenever the repeater E is used for' such purpose the differential relay (S0 be energized to prevent the impulses from crossing from one side to the other. Considering now the effect of the impulses to the trunk conductors a and Z) individually, it will be explained that first the connector switchshaft is raised and next the side switch is tripped to second position by the impulses that have been delivered, corresponding to the second digit 2. rPhe vertical line relay of the repeater E was operated twice and two impulses were delivered to the vertical trunk conductor a from the repeater ground G7. These impulses continue over the vertical trunk conductor a to the vertical line relay 73 (Fig. 3) of the connector F, thence through the winding 76 of' the differential relay 75 to the battery lead 140, and through battery b3 to ground In this case not only the vertical line relay 73 but the differential relay 75 also energizes, the latter to no effect as yet. When the vertical line relay 73 energizes, the springs 141 and 142 then engage, establishing a circuit through the vertical magnet 81 from ground G8 through the springs 142 and 141, through the private springs 143 and 144 to the side switch wiper 86, thence to the contact point 145 and through. the vertical magnet 81 to the battery lead 140, thence through battery Z2 to ground g3. The vertical magnet 8.1 attracts its armature and raises the shaft 67 two steps, lifting the wipers 68, 69 and 70 opposite thev first contact of the second level of the line and private banks 71 and 72. By grounding the rotary line conductor 91 the rotary line relay 59 of the repeater E was energized, as described, the said rela-y in turn delivering a. ground impulse to the rotary trunk conductor Z) trom the.y repeater ground titl Leonesa G7 to the said conductor. 'lhe said impulse continues to the connector rotary line relay 74. thence through said relay and through the winding 7T ot' the diii'erential relay T5 to the back-bridge relay springs 146 and 14T. thence to the battery lead 140, and through battery b3 to ground g3. 'lhe (litten ential and rotary line relays and 74 energize. but the former to no effect, while the latter in pressing the springs 148 and 142 into contact energizes the private magnet 84. which latter then permits the side switch (il to pass to second position. rlhe circuit through the private magnet extends from the connector ground G8 through the said springs 142 and 148, thence through the private magnet 84 and through the springs 146 and 147 of the back-bridge relay 78 to the battery lead 140, and through battery b to ground g3.

The third digit being 0, after the connctor side switch passes to second position the subscriber atthe substation C operates his calling device in accordance with the said third digit of the desired number. 'lhe vertical line conductor 90 is grounded ten times, the vertical line relay 58 of the rcpeater is energized ten times, and as a result the vertical trunk conductor a is grounded ten times and, therefore, the vertical line relay 73 of the connector lF ten times. Since the connector side switch G is now in second position and the side switch wiper'88 is in engagement with the contact point 149, the operation of the said vertical line relay 73 atlects the rotary magnet 82, instead of the vertical magnet 81 as in the previous instance. rlhe said rotary magnet is energized by a current-dow from the connector ground G8 through the springs 142 and 141, private springs 143 and 144 tothe side switch wiper 86. thence to the contact point 149 and through the rotary magnet 82 to the battery lead 140, thence through battery b3 to ground g3. rlhe rotary magnet then operates to rotate the switch-shaft 67 ten steps, carrying the wipers 68. 69 and 7l) into engagement with the tenth terminal ot the second bank level and, therefore, into engagement with the normal line conductors 150 and 151, and with the private normal conductor 152, the line wipers with the tormer set, and the private wipers with the latter. The said normal line conductors 150 and 151 extend through the selector D tothe called subscribers station #220, but the private normal conductor 152 terminates inthe said selector D". When the subscriber grounds the rotary line conductor 91 tor the last time the rotary line relay of the repeater E is energized, deliverin a ground impulse to the rotary trunk conc uctor as before. The edect or this ini ulse may produce either one ot two resu ts, namely the busy release oit the connector switch il? the desired line is busy. or the release ot' the connector side switch to third position and. therefore, the tinal connection between the calling and called Subscribers lilies it said called-line is not busy. lt will first be con sidered how the connection is established. lf the line is not busy the ground impulse delivered to the rotary trunk conductor 7) is sent through the rotary line relay 74 of the connector over circuits that have already been described, which relay in turn encrgizes the private magnet 84 again, tripping the side switch G into third position at the instant that the private magnet 84 de'e'nergizes. The subscribers extended line conductors (t and I) are thus placed in connection with the normal or called subscribers extended conductors 150 and 151 over the following` path: From the conductor a through the condenser 153` conductor 154, side switch wiper 88, contact point 155, conductor 156. vertical line wiper 68 to the vertical normal conductor 150. rlhe rotary trunk conductor is connected through the condenser 157, conductor 158, ringer relay springs 159 and 160 to the side switch wiper 89, contact point 161, conductor 162, rotary line wiper 69 to the rotary normal conductor 151. Furthermore, when the side switch passes to third position the side switch wiper 87 engages the grounded contact point 199, establishing a guarding potential at all contacts connected to the private normal conductor 152. Furthermore, the said guarding potential sets up a tlow of current through the bridge-cut-od' relay 211 of the called selector D. through the said relay to the non-grounded terminal ot battery 53, wliereb)v the line relays 215 and 216 are disconnected trom. across the conductors 150 and 151. Assuming now that the desired line is busy. there will, of course, be lound a guarding potential at the private normal conductor 152, tor the same reasons described in the matter immediately preceding, 4which guarding potential appears at all private bank contacts connected to the said conductor 152. The private wipe'r 70 has already been carried into engagement with the said grounded conductor 152 by the rotation ofi" the shaft 67. as already explained. and since the side switch is in secondiposition and the side switch wiper 87, therefore, in engagement with the Contact point 163.

the private magnet spring 164. which is conl nected with 'the private wiper '111, is also provided with the guarding potential with which the private normal conductor 152 is charged. l't will be noticed. furthermore, that the adjacent private magnet spring 165 is connected with the release magnet 85, which latter is in turn connected with differential relay spring 155 and adapted to be connected with the nonrounded terminal ot battery lo when the e.

relay 75 is energized. Therefore, When the last rotary impulse comes in and the rotary line relay 74 energizes the private magnet 84, as described, the said private springs 164 and 165 are brought into engagement and the differential relay springs 166 and 167 also come into engagement, since the said'differential relay is energized in series with the rotary line relay 74, and as a re sult a flow of current is sent through the release magnet 83. The current flows from the said grounded private contact to the private wiper 7,0, thence through the side switch wiper 87, contact point 163, private springs 164 and 165 to the release magnet 83, thence through the difilerential relay springs 166 and 167 to the battery lead 140, and through battery b3 to ground g3. The release magnet upon energizing restores the switch-shaft 67 and also .the s1de switch G. Therefore, when the subscriber presses his signaling button 31 and grounds the vertical line conductor 91 by carrying the spring 30 onto the grounded contact point 32, the vertical line relay 73 at the connector F is energized and the vertical magnet 81 operated to raise the switch-shaft. As soon as this occursjthe switch-shaft springs 168 and 169 close and abusy signaling circuit is established through the calling subscribers station, for notifying the said subscriber that the desired line is busy. This busy current iows from any suitable busy machine H to the springs 168 and 169,l thence through the side switch wiper 89, ringer re lay springs `160 and 159, condenser 157, trunk conductor b, relay springs 123 and 124 at the repeater E, condenser 65 to the subscribers vertical line conductor 90, thence through the transmitter 23 and primary winding 25 to the rotary line conductor 91 and to the condenser 66 at the repeater E, thence through the relay springs 125 and 126 to the vertical trunk conductor a, through the vertical line relay 73 and winding 76 of the differential relay 75 to the battery lead 140 and back to the busy machine H. The busy current in passing through the primary winding 25 of the induction-coil 24 induces a similar current in the secondary winding 26, which current in passing through the receiver 21 is heard by the subscriber. The subscriber understanding that the line is busy hangs up his receiver 21, which causes the switclrhook 22 to descend, and the cam arm 170 of the latter engages the release spring 42 and presses it onto the springs 41 and 40, whereby simultaneous gro'und impulses are delivered to the vertical and rotary line conductors 90 and 91 for releasing the switching apparatus. The ground circuit to the said line conductors extends from the sub station ground G2 to the ground release spring 40, thence to the release springs 41 and 42 to the vertical and rotary line conductors 90 and 91. As a -result of grounding the said line conductors the vertical and rotary line relays 58 and 59 and the differential relay 60 of the repeater E become energized simultaneously, with the following results: The outgoing vertical and ro tary trunk conductors L and b are grounded simultaneously over circuits already described; the trunk-release springs 171 and 172 of the repeater E are brought into contact, and the differential relay springs 173 and 174 are brought into contact at the same time. The effect of grounding the outgoing trunk conductors a and simultaneously will presently be considered. The effect of the closure of contact between the trunkrelease springs 171 and 172 at the same time that the differential relay springs 173 and 174 close contact is to establish an energizing circuit with the back-release relay 52 of the selector D. The path of the current can be followed from ground G5 -at the side switch of the selector D to the side switch wiper 56, back-release relay 52, conductor 175, private wiper 45, trunk-release springs 171 and 172, resistance-coil 176, differential relay springs 173 and 174 to the battery lead 97, and through battery b2 to ground g2. The back-release relay 52 of the selector D upon attracting its arma-ture presses the back-release relay springs 177 and 178 together, energizing the release magnet 51 from ground G9 through the springs 178 and 177 to the release magnet 51, thence to the battery lead 97 and through battery b2 to ground g2. The release magnet 51 then attracts its armature and remains energized until the substation release springs 40, 41 and 42 separate, in readiness to release the switch at such a time. The simultaneous grounding of the trunk conductors a and b, when the repeater line relays 58 and 59 are simultaneously energized, produces in turn the energization of the vertical and rotary line relays 73 and 74 of the connector F and of the differential relay 75 over circuits that have already been pointed out. is a result the trunk-release springs 179 and 180 controlled by the line relays 73 and 74 are brought into contact at the same time that the differential relay springs 166 and 167 are in engagement. Therefore, the release magnet 83 of the connector 'F is energized by a flow of current from ground GrE through the trunk-release springs 179 and 180 to the release magnet 83, thence through the differential relay springs 166 and 167 to the battery lead 140, and through battery b3 to ground g3. The release magnet upon attracting its armature releases'the connector switch-shaft and side switch, and the magnets remain energized until the release springs at the substation separate. As soon as the said springs separate, the line relays 58 and 59 and the differential relay 6() at the repeater E Adeenergize, destroying the trunk-release circuit through the back-release relay of the selector D and removing the ground connections from the vertical and rotary trunk conductors a and Z). rll`he latter result produces a denergization of all of the energized magnets in the connector switch F, whereby all the magnets of said switch are restored. The removal of the energized circuit through the back-release relay 52 of the selector D produces a denergization of said relay, which in turn produces the denergization of the release magnet 51 and a restoration of the selector switch.

Returning t0 that point where the aut0- matic subscriber established connection with the desired subscriber, as explained. it will now be described how the called subscriber is signa-led by the calling subscriber.

To signal, the his signaling button 29 and grounds the ver,- tical line conductor 90, as already explained. :1s `a result the vertical line relay 73 of the connector F and the differential relay energize simultaneously, the former pressing the springs 141 and 142 into contact, and the latter pressing the springs 166 and 167 into contact. As a result the ringer relay becomes energized by a tlow ot' current from ,round G8 through the springs 142 and 14,1, and through the private springs 143 and 11a to the side switch wiper 86, thence through the contact point 181, ringer relay 85, conductor 182, diderential relay springs 166 and 167 to the battery lead 140, and through battery 53 to ground g3. The ringer relay 85 then attracts its armature and carries the springs 160 and 183 onto the ringer springs 181 and 185. A signaling current is then sent through the ringer 1.86 at the substation #226 trom the ringer generator 187 to the ringer relay spring 185, thence to the spring 183, side switch wiper 88, contact point 155, vert-ical line Wiper 68, vertical normal conductor vertical line conductor 188, through the condenser 189 and ringer 186 to the springs 190 and 191, thence to the rotary line conductor 192. rotary normal conductor 151, rotary line wiper 69, contact point 161, side switch wiper 89, ringer relay springs and 181@ to the ringer generator 187. The subscriber, upon hearing his bell 186 ring, removes his receiver 193, thereby breaking the circuit through the ringer 186 and bridging across the line, instead, the transmitter 19t and the primary winding 195 ot the induction-coil 196 when the springs 197 and 198 close in contact. As soon as the said circuit is closed the bachbridge relay 7 8 at the connector F is energized by a tlow ot current trom the connector side switch ground 111 to the contact point 199, side switch wiper 87 through the calling subscriber pressesl 'does winding 80 ot the said relay 78, and through the ringer relay springs 159 and 160 to the side switch wiper 89, contact point 161, rotary line wiper 69, rotary normal conductor 151, rotary line conductor 192, primary Winding 195, transmitter 194, primary circuit springs 198 and 197 to the vertical line conductor 188, vertical normal conductor 1 50, vertical line wiper 68, contact point 155,

side switch Wiper 88, winding 79 of the relay 78, and through the differential relay springs200 and 167 that are normally in contact to the battery lead 140, thence through battery b3 to ground (/3. The called subscriber is thus provided with talking battery current upon answering, and at the same time energizes the back-bridge relay 78 to provide the calling'subscriber with talking battery current. The latter circuit is established as soon as the back-bridge relay 78 presses the springs 116 and 201 into engagement and energizes the pole-changing relay 63 at the repeater E. The current flows from the connector side switch ground G10 to the contact point 199 and side switch wiper 87, thence through the said backbridge relay springs 201 and 146 and through the winding 77 of the dititerential relay 75 and the rotary line relay 74 to the rotary trunk conductor b, thence through the springs 123 and 1211 of the relay 61 at the repeater E, thence through the springs 139 and 138 of the dierential relay 60 to the pole-changing'relay 63, springs 125 and 126 ot the auxiliary relay 64 to the vertical trunk conductor a, thence through the vertical line relay 73 at the connector F, and through the winding 76 of the differential relay 75 to the battery lead 1110, thence through battery 53 to ground (73. 1l' ot only the pole-changing relay 63 energize in this circuit. but the line relays 73 and 749i ot the connector F energize also, and the trunkrel'ease springs 179 and 180 are brought `into engagement; but the release or the connector does not occur, because the differential relay 75 does not energize, since the current through the windings 76 and 77 ot the said relay is passing in such a manner as to render the magnetic torce oit no ehect. When the pole-changing relay at the repeater E energizes, the connection between the .line

`relay springs 128 and 135 and the respective vertical and rotary trunk conductors a, and 5 is broken, and the springs 137 and 136 separate. Furthermore, when the spring 133 shifts away trom the spring 1341 and into engagement with the spring 2041-, a circuit is 'established through the transmitter 33 ot the calling subscriber tor providing the said subscriber with talking battery current. The circuit extends from ground G@ through the springs 2041 and 133, winding 62 ot the ditlierential relay 66, rotary line relay 59 to the rotary when the springs 130 and 131 Y line conductor 91, thence through the primary winding 25 and transmitter 23 at the substation C to the vertical line conductor 90, thenceto the vertical line relay 58 of the repeater E, and througi the winding 61 of the differential relay 60 to the battery lead 97 thence through battery b2 to ground g2. The subscribers after being thus provided with talking battery current may communicate with each other over the heavily marked conductors between the substations C and C (shown in Figs. 1 and 2), namely the conductors 90 and 91, and through the-condensers and 66 at the repeater E, vertical and rotary trunk conductors a and, b, condensers 153 and 157 at the connector F to the vertical and rotary line conductors 188 and 192 of the called subscribers line. lt will be understood, of course, that the calling subscribers line is protected against interference by other subscribers who might attempt to connect with his line while he is busy, by a guarding potential that is established by way of the private normal conductor 205 of the selector D to the connector banks, which conductor 205 is directly connected to the switch-shaft spring 206. When the switchshaft rises the normal post arm 207 on said shaft, upon rising, permits the spring 206 to engage the grounded contact point 208, thus establishing a guarding potential from ground G11. When the switch is in normal position, however, the subscriber at the substation G may be called by any other automatic subscriber over the normal line conductors 209 and 210, just as the subscriber #220 is called over the normal conductors 150 and 151. rlfhe called subscriber is, of course, protected by a guarding otential that appears at the private wiper 0 when the side switch wiper 87 passes to third position and engages the grounded contact point 199. -This guarding potential appears at the private normal conductor 152 and at all private bank contacts connected in multiple therewith. Said guarding potential not only prevents interference from other subscribers, but also causes the energization of the bridge-cutoff relay 211 at the called selector D', whereby the bridge-cutoff relay springs 212, 213 and 2111 are separated fon disconnecting the line relays 215 and 210 .from across-the line and for disconnecting them also from the battery lf. After the subscribers are through talkingthe connection may be destroyed by the calling subscriber when he hangs up his receiver and grounds the vertical and rotary line conductors 90 and 91 simultaneously. The circuits involved in the release after the called subscriber has answered are a trifle different from those involved before the subscriber has answered, or at any time when the switch-hook of said called subscriber is in normal position. Since the calling sub- Leonesa scribers transmitter is provided with talking battery current through the line relays 58 and 59 of the repeater E, as described, the said relays, like the relays 7 3 and 711 of the connector F, are energized during talking; but the diderential relay 60 does not energize for obvious reasons. rlherefore, since the extended end of the rotary line conductor 91 is grounded at ground G while the subscribers are talking, when the release comes in and the said rotary line conductor 91, together with the vertical line conductor 90, is grounded,-the rotary line relay 59 at the repeater E and the winding 62 of the diderential relay 60 are short -circuited through ground between the ground terminals G6 at the repeater E and G2 at the substation C. Therefore, the How of current through said windings is cut od' and the differential relay 60 energizes. When the said relay energizes, the diderential'relay springs 138 and 139 are separated, so that the circuit of the pole-changing relay 63 is broken and the said relay returns As a result the springs gage, and also the springs 136 and 137, and furthermore the spring 133 leaves the ground spring 204: and returns into engagement with the s ring 13d. 'llhe rotary line conductor 91 being still grounded, the rotary line relay 59 is now renergized, and a flow of current is set up through the winding 62 of the diderential relay 60 in a reverse direction from the original current flowing therein, so that the already energized differential relay is further strengthcned. As the rotary line relay 59 energizes, the trunk-release springs 171 and 172 come into contact while the `diderential relay springs 173 and 17d are in engagement. l,Therefore the trunk-release circuit through the back-release relay 52 of the selector D is established, as already explained, with the results already pointed out. The energizing circuit for the pole-changing relay 63 at the repeater 1E being destroyed when the diderential relay 60 is energized, as enlained, the vertical and rotary line relays 3 and 74.- 'dif the connector F also de'energizefor a moment, since said relays G3, 73 and 74; are i a series circuit, as explained; but as soon as the connection is restablished between the line relay springs 128 and 135 of the repeater E and the trunk conductors a and respectively, when the relay 83 deenergizes and the rotary line relay 59 of the repeater renergizes, as explained, the trunk conductors a and t are grounded simultaneously, as in the previous instance and, therefore, the line relays 73 and 7d of the connector li renergize, carrying the trunk-release springs 179 and 130 into contact, and the diderential relay 75 is also energized. The result is that the connector release niagnet 33 is operated, as before, and the con- 130 and 131 will ento normal condition.

'lamp 202 to ground G13.

Lacasse nector switch-shaft and side switch are restored. .The connection is therefore broken between the switch-shaft wipers and the normal conductors 150, 151 and 152, whereby a' disconnection is obtained from the called line and the energizing circuit through the bridge-cut-ol'l1 relay 211 of the selector D is also. destroyed, whereby thesaid relay denergizes, permitting the bridge-cut-of relay springs 212, 213 and 214 to rengage. As soon as the substation release springs'40, 41 and 42 separate, the full restoration of the switching apparatus then fol-lows, as already explained. 0f course, in every instance of a release, when the connection is broken between the selector D and the repeater' E, the auxiliary relay 64 deenergizes and the supervisory lamp 18 at -the cord circuit B goes out as a signal to the manual operator that the trunk is no longer busy.

1f the manual subscriber alloted to the cord circuit A (Fig. 1) wishes to callthe automatic subscriber #220, for example, he removes his receiver and a signal is thus given to his manual operator A who takes his order from him. She then operates the order key e, causing the lamp 202 to flash up, when the springs 218 and 219 close and signal the trunking operator B. The circuit through said lamp 202 extends from ground G12 through the battery 217, and through the springs 218 and ,219 of the order key e to the 'springs 220 and221 ofthe key n at the operators cord 13, thence through the The .operator at the cord circuit A presses her key e in order to converse with the operator at B when the latter presses the key n. 1t will be understood that when thekey e is pressed the springs 222 and 223, and 230 and 229 close in contact, respectively, and at the key n the springs 224 and 225, and 227 and 228, respectively, engage, and the springs 221 and 220disengage when said key n is pressed. The talking circuit for said operators eX- tends from the receiver 6 at the cord circuit A. through the secondary winding 8 of the inductionoil j", through the springs 222 and 223 to the springs 224 and 225 at .the key n., thence through the receiver 226 at the oord circuit B, through thesecondary Winding 17 to the springs 227 and 228, thence to the springs 229 and 230 back to the receiver 6. rlFhe transmitters 5 and 15 of the respective operators are, of course, includedin local circuits comprising the primary windings, in the usual manner. rllhe operator B, when she cornes on the line,` instructs the operator A to come in on a certain trunkfor exam ple,the trunk leading from the jack j. las soon as the plugsT is inserted into the jack j the back supervisory relay 3 of the cord cir- A is energ' ed by a liiovv of through the resistance coil 231, through the repeating coil Winding 12 to the sleeve spring 232 of the jack j, thence to the sleeve 233 of the plug d, to the supervisory relay 3 and through battery B. r1`he said relay upon energizing attracts the armature 234, lighting the lamp 235. Furthermore, the insertion of the said plug d in the jack j presses the springs 236 and 237 into contact, whereby the relay 238 is energized by a 'How of current fron"1"ground Great the repeater E through the auxiliary relay springs 119 and 120, conductor 239, relay 238, springs 236 and 23.7 to the battery lead 118, thence through battery B to ground Gr. Said relay 238 upon attracting the armature 240 onto the contact point 241 lights the supervisory lamp 18. The circuit for lighting said lamp extends from ground G15 at' the cord circuit B through the armature 240, contact 241 and lamp 18 to the battery lead 118, and through battery B to ground G. The operator at the cord circuit ll is, therefore, informed as soon as the operator at the cord circuit A seizes thetrunk. Another circuit is, furthermore, said relay 238 carries the other armature 242 into engagement with the contact point 243, whereby the auxiliary relay 20 of the cord circuit B is energized from ground G15 through the armature 242 and contact point 243 to the relay 20, thence through said relay to the battery lead 118, and through battery B to ground Gr.- Y Said relay 20 then attracts its armatures 244, 245 and 11'? onto the respective contact points 246, 24? and 248. The engagement of the armatures 244 and 245 with the Contact points 246 and 247 connects-the tip and sleeve conductors 249 and 250 of the cord circuit H with the outgoing trunk conductors a andi),- and the engagelnentof the armature 117 with the contact point 248 energizes the auxiliary relay 19 at the cord circuit B, by a dow of current from ground G1 through the said relay 19 to the contact point 248, thence through the armature 117 'to the battery lead 118, and through battery B to ground G. The said relay 19 then attracts its armatures 251, 252 and 253, carrying them into engagement with the contact points 254, 255y and 256, respectively. The closure of connection between the armature 252 and contact point 254 establishes a guarding potential at the private trunk conductor 110 between the repeater 1E and the selector banks. Therefore, all the private bank contacts connected with said private trunk conductor are provided. with a guarding potential to prevent any automatic subscriber from coming1 in on line. The circuit over whicl pot is estabiished is as follows:

im the ccrd circuit a 'the established when the i all private bank contacts connected therewith. Meanwhile the operator at the cord circuit B proceeds to call the desired subscriber by shifting her key o, whereby the spring 257 is carried into en agement with the spring 258, and the sprlng 259 disengaged from the spring 260 and pushed against the spring 261. Furthermore, the spring 262 is disconnected from the spring 263 and placed in engagement with the spring 264, and the springs 114 and 115 are separated. Should the operator at the cord circuit A delay in plugging in the jack j, the operator at the cord circuit B secures the outgoing trunk comprising the conductors a. and b as soon as the said springs 257 and are carried into contact by the operator at the cord circuit B when'the key o is oper ated, as described. In that case the auxiliary relay 20 is energized from the ground *G17 at the key o, through the said springs 258 and 257 and through the coil 20 to the battery lead 118. The said relay 20, of course, attracts its armatures, as already eX- plained, establishing a guarding potential at the selector private bank contacts, as already pointed out. After the trunk line is thus once seized the operator at the cord circuit B does not release her key 0 until she Sees the lamp 18 flash up, indicating to her that the operator at the cord circuit A has plugged in. rl`he operator at the cord circuit B in the meantime proceeds to call the desired number which, has been given to said operator over the order wire. The separation of the springs 259 and 262 from the springs 260 and 263, respectively, disconnects the tip and sleeve conductors 249 and `250 from the trunk conductors a and Z), and the engagement of said springs 259 and 262 with the springs 261 and 264 places the trunk line conductors b and a in connection with the automatic calling device fm and with the springs 265 and 266 thereof, Since the operator at the cord circuit B is thus connected direct with the trunk line conductors a and it is only necessary for her to operate her calling device m in accordance with the last digits 2 and 0, since the trunking operation corresponding to the trunking operation of the selector D in the preceding case, to reach the trunk conductors n. and I), is perfornied by the manual operators A and B. The operator B, therefore, presses her vertical button 267 twice. pushing the spring 266 against theground spring 268 and sending two ground impulses to the vertical trunk conductor a, operating the connector vertical line relay 73, as already understood, by a flow of current from ground G18 through the springs 268 and 266 and springs 264 and 262, contact 247 and armature 245 to the vertical trunk conductor a., thence through the vertical linel relay 73 at the connector F, winding 76 of recrear and 265 and springs 261 and 259, contact point trunk conductor b. Therefore, the rotary line relay 74 at the connector F is energized, which in turn energizes the private magnet 81, tripping the side switch Gr to second position. rlhe operator then proceeds to press the vertical spring 266 ten times in accordance with the digit 0, thereby grounding the vertical trunk conductor a ten times and operating the vertical line relay 73 at the connector F ten times, whereby the rotary magnet 82 is energized ten times to so rotate the switch-shaft 67 as to carry the Wipers es, mal conductors 150, 151 and 152, respectively. When the rotary button 265 is pressed lfor the last time, if the line is busy the connector is released, as already explained; and then when the vertical .button 267 is pressed, in order to ground the vertical trunk conductor a for signaling, the busy signaling circuit is established, as already stated, when the switch-shaft 67 is raised and the switch-shaft springs 168 and 169 close in contact. Assuming that thev operator at the cord circuit A has plugged in and extended the calling subscriber-"s telephone line with the cord circuit lB, the operator at the said cord circuit B, after performing the required operations, releases the key c, thus connecting the calling subscriber with the trunk conductorsl a and 5 over circuits 'marked by the heavy conductors shown in Fig. 1. The busy signaling current then reaches the rotary trunk conductor 5 over circuits already conductor 270, to the armature 24:4, of the relay 2O at the cord circuit B, thence to the contact point 216, springs 259 and 269 to the sleeve conductor 249, thence through the winding 13 of the repeating coil 7c, condenser 271, repeating coil Winding 14, sleeve conductor 250, springs 263 and 262, contact vpoint 2-17, armature 245 and back to the vertical trunk conductor a. The current is, of course, induced in the windings 11 and 12 of the repeating coil ic, from whence it eatends to the cord circuit A and through the condensers 9 and 10 tothe calling subscrib: ers station. Upon hearing the signal the calling subscriber hangs up his receiver, causing the front supervisory lamp (not shown) at the cord circuit A to Hash up, giving the operator the disconnect signal. The operator then withdraws the-plug Z from the jack j, thereby breaking the ener- 246 and armature 2114 to the rotary 69 and 70 into engagement With the norknown and passes to the i fie led from ground G16,

Leonesa gizing circuit through the back supervisory relay 3,. which permits the lamp 235 to go out, and also the springs 236 and 4237 at the cord circuit B to separate on the Withdrawal of the plug d', and the relay 238 is denergized as a result. The lamp 18 then goes out, since the armature 240 leaves the contact point 241, and when the .armature 242 leaves the contact point 243 the relay 20 deenergizes, said relay causing the denergization of the relay 19 which it controls. 'lhe relay 20, however, is al quiclcacting relay, while the relay 19 is a slowacting relay, and as soon as the armatures 2tland 2dr-5 ot the quick-acting relay return into engagement with the vcontact points 272anol 273, the vertical and rotary trunk conductors a and b are simultaneously ground- Which ground connection is controlled by the slow-acting relay 19. The impulses to the said conductors@ and b pass over the following paths: From ground G16 to the contact point'255, armature 251 ot the slow-acting relay, contact 272 and armature 24flol the quicliacting relay to the conductor 270, and thence to the rotary trunk conductor The other path tor the ground impulses is from ground G16 to the contact point 250 and ari-nature 253 ot slow-acting relay' to the Contact point 273 andiy armature 2&5 or the quiclia-cting relay to the verticaltrunlr conductor u. its result the connector switch l? is released, as already describedo lt, however, instead or the line being busy the connector side switch passes to third position, then when the vertical trunk conductor a, is grounded, and when the operator presses the spring 230 onto the ground spring 203 to signal the called subscriber, after the connection is completed, the ringer relay 35 is operated as betere. 'lhe called subscriber is thus notied that he is called; then Twhen he answers he receives talking current through the back-bridge relay 7 8 of the conhector l?, as previously described,` Which re lay in turn, upon shitting the spring M0 onto the ground spring 20l, establishes a circuit through the relay 27e at the cord circuit B for energizing the supervisory relay 2 at the cord circuit il. and tor eatin guishing the lam 235. The circuit through the said relay 27j/l begins with the ground terminal G10 at the connector side switch, thence to the contact point 199, side switch `Wiper 87, back-bridge relay springs .201 and 146, thence through the Winding 77 ol' the differential relay 75, rotary line relay 7lto the rotary trunk of the conductor 27 0 to the armature 24rd of the quick-acting relay 20 at the cord circuit B, Contact point 2-l6 to the relay 27d thence through said relay to the contact point 2l7 and armature 2l5 ot the quick-actin relay 20, to the vertical trunlr conductor a, thence conductor h, thence by Way' Lil to the vertical line relay 73 of the connector l" and through the winding 76 of the diderential relay 75 to the battery lead 14:0, and through battery b3 to ground g3. The relay 274 at the cord circuit B upon attracting its armature 275 onto the contact point 27 0 energizes the supervisory relay 2 at the cord circuit A by establishing a circuit from the non-grounded terminal of battery B at the cord circuit flkthrough the supervisory relay 3 to the sleeve 23,3 of the plug d, thence to the sleere spring 232 of the plug j, to the Winding 12 ot the repeating coil I: at the cord circuit B, to the contact point 276 and arrnature 275 ot the relay 274:, thence through the repeater Winding ll to the tip spring 277 of the jaclr @thence to the tip conductor 278 of the cord circuit it,

ture 279, contact 280 ot the supervisory relay 3 to the supervisory relay 2, thence n through said relay to ground G. 1When said relay attracts its armature 23l armature leaves the contact point 232, brea t. ing the circuit of the lanip 235, which lai p signal then, or course, disappears, indicating to the operator that the called subecrib has answered. ...fitter the subscribers 'through tallri'ng they inay restore their receirers, the calling subscriber thus givingl a disconnect signa-l to operator A, and the sending a. disconnect sigcallecl subscriber nal to the operator also, when the relay 2 denergiaes.. This, ot course, occurs when the subscriber destroys the energizing circuit through the bach-bridge relay 73 o n th connector l?, which in turn upon fall if" 'back and permitting' the springs ai to separate causes the denergiaation of relay at the cord circuit i J in turn causes the dee'nergization of the supervisory relay 2 at the cord circuit il, at which tir-ne the bach supervisory lamp 235 flashes up again. @t course, when the crater A withdraws the plug 0l, the release ol"a the switches follows, as before, from the denergizaticn of the relay 233 ol" the cord circuit ll, and the subsequent denergization or' the quiclr and slow acting relays 20 and 10, as before. Alter the operator at the trunlring circuit B operates the key o to conneet the calling and called subscribers, then it the called subscriber does not answer, the operator at the cord circuit A may signal the called subscriber by pressing the signaling key q, in which case the ringer generator a, which is normally grounded at i12-is bridged across the tip and sleeve. springs 232 and 277 of the cord circuit B, and the signaling relay p at the said cord circuit E is energized. Thus the armature 203 is oar-A ried away `trom the contact point 233 and into engagement with the ground terminal G2. The effect ol.E thus operating the relay p to disconnect the bridge formed through the relay 27aacross the tipv and. sleeve con- 'im lllall ill...

ductors 249 and 250, grounding the latter and, therefore, grounding the vertical trunk conductor a, whereby the ringer relay 85 at the connector F is energized, as already known, for signaling the called subscriber. The alternating current signaling relay p, of course, may be of any suitable design that will accomplish the purposes set forth.

From the foregoing it will be seen that l provide a highly improved combined manual and automatic system whereby automatic subscribers may call automatic subscribers over a given trunk line to which the manual operators also have access, giving a certain class of said operators a signal when the trunk line is brought into use; a highly improved system in which manual subscribers may not only matic subscribers as well, through a trunkiiig operator B, the line operator A being given total supervision over the connection after the trunking operator has established the connection.

In the repeater E it is found that the resistance of the coils may be varied, but good results are obtained when the line relays 58 and 59 are wound to one hundred ohms each; the windings 61 and 62 of the di fferential relay to two hundred and fifty ohms each; the pole-changing relay 63 to five hundred ohms; the auxiliary relay 64: to thirteen hundred ohms. In the cord circuit B the coil 231 may be wound to live hundred ohms; the coil 238 to one thousand ohms; the quickacting relay 20 to two hundred and fifty ohms; and the slow-actiiig relay 19 to two hundred and fifty ohms.

As far as the broad idea of both manually and automatically trunking over a trunk line in the same. direction to call an automatic subscriber is concerned, the details can be changed or varied without departing yfrom the spirit of my invention.

rl`he connectors can be employed on a percentage basis, and may thus be less in nuinber than the subscribers 'having access to them. The first-selectors can also be reduced to a percentage basis in any suitable or known manner, and second and third selectors can be employed if necessary. ln this way automatic trunking is alieorded in a system .in which a trunk line can be used by either a manual or an automatic subscriber for getting connection with the line ot an automatic subscriber.

is indicated in Fig. 1 the jack j will have as many multiples thereof as there are operators switching positions' at the manual board. ln this way each manual or originating operator will have access to each lof the different trunlring operators cord circuits allotted to the diiiierent outgoing trunks extending to the other exchange-that is say, the different outgoing trunlrs having call each other, but the auto- Leones-4i peaters E throtugh the medium offwliich the calling automatic subscribers control the automatic switches at the other exchange. lVith the arrangement shown, one or more levels in the first-selector D can be reserved for the outgoing trunk lines leading to the said other exchange, and all other levels can then be used for establishing connection between automatic subscribers of the main exchange. In this Way, as explained, automatic and manual trunking is atlored in a common battery telephone system having provisions by which either a manual or an automatic subscriber can employ the same trunk line for obtaining connection with the line of an automatic subscriber at another exchange.

What l claim as my invention is l. ln a telephone exchange system, the

combination of a trunk line, an automatic' switch attheend of said line, a subscribers calling mechanism for controlling said switch over said trunk line, means responsive to the calling subscriber for automatically seizing the trunk line, means for manually connecting with said line, an operators calling mechanism for controlling said switch over said line, and means for preventing autoinatic selection of said trunk line when it is in use for connecting a manual subscribers linel with an automatic subscribers'line.

ln a telephone exchange systemy thecombination of an automatic switch, a trunk line leading to said switch, an automatic selector switch responsive to the calling subscriber for connecting with the other end of said trunk line, a manual switchboard apparatus for connecting with said trunk line, a subscribers calling mechanism for controlling botli of said switches, an operators calling mechanism for controlling the rstmentioned switch, and means for preventing automatic selection of said trunk line when it is in use for connecting a manual subscribers line with an automatic subscribers line.

3. A. trunk line, a spring ack for one end' of said trunk line, a selector provided with a bank terminal of said line, an automatic switch individual to and in which the other end of said line terminates, and a trunlin operators cord circuit for connecting sait jack with said trunlr line.

4. l trunk line, a. spring jack for one end ot said trunk line, a selector provided 'with a bank terminal of said line, an automatic i switch individual to and in which the other end opt said line terminates, a snbscriberas calling mechanism for operating said selector and automatic switch, an operators calling mechanism for operating said automatic switch, a manual switchboard provided with. a cord and plug adapted for insertion in said jack, and a truiilting operatorls cord circuit lll@ lll)

lli

lili

lill

peater individual to said trunk line, an automatic switch individual to said trunk line, a subscribers callin@ mechanism for controlling said switch through the medium of said repeater, and a trunking operators cord circuit individual to said trunk line.

15. ln a telephone exchange system, the4 combination of multiple jacks, a trunking operators cord circuit to which said jacks are individual, and an outgoing trunk line to which the said cord circuit is individual, said cord circuit constituting the medium of connection between the said trunk line and jacks.

16. In a telephone exchange system, the combination of a trunk line, an automatic switch, a trunking operators cord circuit, an originating operators cord circuit, means by which the trunking operator controls the said automatic switch over the trunk line, and means by which a disconnection of cord circuit from the other automatically releases the said automatic switch.

i7. lna telephone exchange system, the combination of a trunk line, an automatic switch, a trunking operators cord circuit, an originating operators cord circuit, means by which the trunking operator controls the said automatic switch over the Crunk line, means by which a disconnection ot one cord circuit from the other automatically releases the said automatic switch, a repeater, and a subscribers calling mechanism for controlling 'said automatic switch through the medium oi said repeater.

18. ln a telephone system divided into groups, the combination of a trunk line, an automatic switch lat the end of said line, a subscribers calling mechanism for controlling said switch over said trunk line, means tor manually connectingI with said line, an operators calling mechanism for controlling said switch over said line, and meanstor indicating that thetrunk line is busy to pre- Vent manual connection therewith, said system being provided with'f'means operative by vertical motion to select roups and by rotary'imotion to connect with the called line in any selected group.

19. ln a telephone system divided into groups, the combination of an automatic -trolling the means for indicating that the trunk kline is switch, a trunk line leading to said switch,

,an automatic switch for connecting with the other 'end ot said trunk line, a manual switchboard apparatus, for connecting with said trunk line, a subscribers calling mechanism tor controlling both ot said switches, an. operators calling mechanism for conlirst -mentioned switch, and

busy to prevent manual connection therewith, said system being provided with means operative by vertical motion to select ou s and by rotary motion to connect with t e called ein any selected group.

Lantana 20. ln a telephone system divided into groups, the combination of a trunk line, a repeater for one end oit said trunk line, an automatic switch for the other end of said trunk line, a sprin jack and a trunking operators cord circuit for the repeater end of the trunk line, a trunking operators calling lmechanism for controlling said automatic switch, an originating operators cord circuit for connecting a callmg manual subscribers line with said ack, an automatic switch toi' connecting with the repeater end oi the trunk line, a subscribers calling mechanism for controlling both of said automatic switches, an order line between the two cord circuits, means by which the originating operator supervises any connection established over said cord circuits and trunk line, and means for preventing automatic selection oi said trunk line when the same is in use for connecting the manual subscribers line with the first-mentioned automatic switch, `said system being provided with means operative by vertical motion to select groups and by rotary motion to connect with the calledl line in any selected group.

21. ln a telephone system including subscribers lines divided into groups, an automatic switch, a repeater provided with a pole-changing relay, an auxiliary relay, relay springs, trunk conductors adapted to be seized by said switch and connections between the said relay springs and said trunk conductors, controlled b said relays, said automatic switch control ed by said repeater and having motion first to select groups and motion to then nd a line in a selected grou n scribers lines divided into groups, the combination of an automatic switch, an outgoing trunk line extending from said switch, a repeater individual to said trunk line, 'an' automatic switch individual to said trunk line, a subscribers calling mechanism tor controlling said switch through the medium ot said repeater, and a trunlring operators circuit individual to said tru-nk line, said lastmentioned automatic switch having motion in one plat/le to select groups and motion in a plane at right-angles thereto to tind a line in a selected group.

23. ln a telephone system including subscribers lines divided into groups, the conibination ot an automatic switch, -multiple jacks, a trunking operators circuit to which said jacks are individual, and an outgoing trunk line extending to said switch to which the said circuit is individual, said circuit constituting the medium ot connectionbetween the said trunk line and jacks, said automatic switch having motion in one plane to select groups and motion in a plane at right-angles thereto to find a line in a selected group.

2li. iin a telephone system including sublim Leonesa scribers lines divided into groups, the cornbination of a trunk line, an automatic switch, a trunking operator-s circuit, an originating operators cord circuit, means by which the trunking operator controls the said automatic switch over the trunk line, and means by which a disconnection of one circuit from the other automatically releases the said automatic switch, said automatic switch having motion in one vplane to select groups and motion in a plane at rightangles thereto to find a line in a selected group.

25. 'In a telephone system, a spring jack, a trunk line terminating at one end in an automatic switch, a connection between said jack and the opposite end of said trunk line, and means by which an operator controls the connection between the jack and trunk line, said jack being allotted to said trunk line.

v26. In a telephone system, an automatic progressively movable switch, a sloweacting relay, means controlled by said relay for automatically establishing a guardin potential to prevent seizure of said switc when the same is in use and for initiating an automatic release of said switch.

27. ln a telephone system, a cord circuit, a relay and a supervisory signal controlled thereby associated with said cord, 4a trunk circuit accessible to said cord, a relay in said trunk for directly controlling the circuit of said iirst-mentioned relay and said signal, anautomatic switch, and means for connecting said switch with said trunk.

28. in a telephone system, an automatic switch, a trunk extending to said switch, said trunk consisting of two parts, one normally connected with said switch and a pair of condensers in the other part, said condensers being normally disconnectedfrom said switch, and means for establishing a talking circuit through said condensers and over said trunk to said switch.

29. liu a telephone system, an automatic switch, a trunk line extending to said switch and normally connected thereto, a second trunk normally disconnected from said first trunk, a repeater in said second trunk, a pair of condensers in said second trunk, and means tor repeating impulses from said first-:to said second trunk and for then connecting said trunks together, whereby said condensers are connected to said automatic switch.

30. In a telephone system, an operators circuit provided with jack springs, a relay having a pair of armatures, means for energizing said relay when connection is made with said circuit, a trunk line normally disconnected from said operators circuit, and a second relay for controlling the connection between said operators circuit and said trunk, said second relay being controlled by said first relay. 31. In a telephone system, an operators circuit provided with Jack springs, a relay having a air of armatures, means for energizing said relay when connection is made with said circuit, a trunk line normally disconnected from said operators circuit, a second relay for controlling the connection be tween said operators circuit and said trunk, said second relay being controlled by said irstrelay, and a supervisory signal controlled by said first relay.

32. In a telephone system, an automatic switch, a slow acting relay, means controlled by said relay for establishing a guarding potential to prevent seizure of said switch by 4another automatic switch and for initiating an automatic release of said switch, said other switch'having access to said first mentioned switch.

33. ln a telephone system, an automatic switch, a trunk line extending to said switch, said trunk line consisting of two parts, one normally connected with said switch, and a pair of condensers in the other part, said Condensers being normally disconnected from said switch, a line relay for controlling said switch, said relay normally connected to said normally connected part of said trunkline, and means for establishing a talking circuit through said condensers and over said trunk line to said switch.

Signed by me at Chicago,'Cook county, llllinois, this 9th day of November 1906.

TALBUT G. MARTliN.

Witnesses:

EDWARD D. Farms, JOHN Enicxson. 

